An infant born at 35 weeks' gestation to a mother with no prenatal care is noted to be jittery and irritable, and is having difficulty feeding. You note coarse tremors on examination. The nurses report a high-pitched cry and note several episodes of diarrhea and emesis. You suspect which of the following?
a) Hypothyroidism
b) Phenylketonuria (PKU)
c) Galactosemia
d) Neonatal abstinence syndrome